Field of the Invention
The present invention relates to an image forming apparatus.
Description of the Related Art
There have been image forming apparatuses that put a fixing roller and a pressure roller into a separated state when the power for heating the fixing roller is turned off (see JP 2011-95692 A, for example).
By the technology disclosed in JP 2011-95692 A, when the heating of the fixing roller is stopped, the fixing roller and the pressure roller are separated from each other, so that a quick recovery to a normal state is possible even in a case where the fixing unit has abruptly stopped due to a jam or the like during conveyance of paper, and the fixing temperature of the fixing roller has risen.
However, the technology disclosed in JP 2011-95692 A relates to a system configuration in which an image forming apparatus does not store any record of problems that have occurred. When the image forming apparatus is restarted after the power is turned off, the record of the past states of the respective components in the image forming apparatus is erased. For example, in a case where the power is turned off after a jam or a service call (SC), and the image forming apparatus is then restarted, or where the power is abruptly turned off due to a blackout or the like, and the image forming apparatus is then restarted, no record of the past states of the respective components in the image forming apparatus is stored, and therefore, the restart is regarded as a recovery to a normal state.
In an image forming apparatus that forms an image on roll paper, even if such a restart is regarded as a recovery to a normal state, it is necessary to introduce roll paper into the image forming apparatus main unit including the fixing unit before a printing operation is performed. In such an image forming apparatus, a normal state is a state where roll paper exists along the conveyance path in the machine at the time when the power is turned on, or is a state where any roll paper does not exist in the conveyance path in the machine at the time when the power is turned on.
However, a state where part of a long paper sheet remains in the conveyance path in the machine when the power is turned on is not a normal state. Therefore, a problem might occur, if a recovery to a normal state is determined regardless of the state of the roll paper in the conveyance path in the machine.
If the fixing temperature of the fixing unit is high, and the roll paper is film-type paper made of polypropylene (PP) or polyethylene terephthalate (PET), the roll paper deforms and melts readily, compared with conventional paper. In view of this, roll paper left in the fixing unit while the fixing temperature is high might deform and melt. If roll paper is conveyed in such a state, various problems might occur.
For example, roll paper being conveyed might leave scratches on the fixing unit. If roll paper melts with heat, the roll paper not only winds around the fixing unit but also causes a problem in winding up the roll paper.